LinqKit predicate builder - Multiple WHERE Clauses with LINQ extension methods

// initial "false" condition just to start "OR" clause with
var predicate = PredicateBuilder.False<YourDataClass>();
if (condition1)
{
    predicate = predicate.Or(d => d.SomeStringProperty == "Tom");
}
if (condition2)
{
    predicate = predicate.Or(d => d.SomeStringProperty == "Alex");
}
if (condition3)
{
    predicate = predicate.And(d => d.SomeIntProperty >= 4);
}
return originalCollection.Where<YourDataClass>(predicate.Compile());

Predicate Builder class

using System;
using System.Linq;
using System.Linq.Expressions;
using System.Collections.Generic;
public static class PredicateBuilder
{
  public static Expression<Func<T, bool>> True<T> ()  { return f => true;  }
  public static Expression<Func<T, bool>> False<T> () { return f => false; }
  public static Expression<Func<T, bool>> Or<T> (this Expression<Func<T, bool>> expr1,
                                                      Expression<Func<T, bool>> expr2)
  {
    var invokedExpr = Expression.Invoke (expr2, expr1.Parameters.Cast<Expression> ());
    return Expression.Lambda<Func<T, bool>>
          (Expression.OrElse (expr1.Body, invokedExpr), expr1.Parameters);
  }
  public static Expression<Func<T, bool>> And<T> (this Expression<Func<T, bool>> expr1,
                                                       Expression<Func<T, bool>> expr2)
  {
    var invokedExpr = Expression.Invoke (expr2, expr1.Parameters.Cast<Expression> ());
    return Expression.Lambda<Func<T, bool>>
          (Expression.AndAlso (expr1.Body, invokedExpr), expr1.Parameters);
  }
}

Source:

http://www.albahari.com/nutshell/predicatebuilder.aspx
http://stackoverflow.com/questions/8791540/multiple-where-clauses-with-linq-extension-methods